What percentage is relative humidity?

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Relative humidity is 35%. What percentage of humidity will there be if the saturated vapor density becomes half as much?

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Source: http://eurasia96.ru/fizika/zid487622.html

What percentage is the relative humidity of the air if the readings of the dry and wet thermometers of the psychrometers are the same? Explain your answer.

If the readings of both thermometers coincide, then relative humidity = 100%, because water cannot evaporate from the cotton wool of a wet thermometer, and therefore cooling

Other questions from the category

At the moment of falling onto the net, the acrobat had a speed of 9 m/s. With what acceleration did the braking occur if the net bent by 1.5 m before the acrobat came to a complete stop?

if you can make it clearer)

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2) the permissible humidity in the museum premises should not exceed 70%. Is this requirement met if the readings of the dry and wet thermometers are 17 and 21 ° C, respectively?

1) What is the temperature of molecular nitrogen in a cylinder with a capacity of 8.3 * 10^-3 m^3, if its mass is 0.14 kg. The pressure exerted on the walls of the cylinder is 35 * 10^5 Pa.

2) Find the relative humidity of the air when the readings of the dry and wet thermometers of the psychrometer are equal to 29 and 22oC, respectively; 15 and 9oC; 25 and 21oC; 20 and 18oC. Compare the found values ​​of relative humidity with the results of readings using a Lambrecht hygrometer, if the dew point values ​​​​indicated by it at the same moments and in the same place are equal to 18; 2; 19; 17 oC, respectively.

3)Relative humidity 73%. What do the dry and wet thermometers of a psychrometer show if the difference in their readings is 2oC? 4oC ?

Please help me solve problem 1, 2 and 3 are optional!!

2) How will the difference between the readings of dry and wet thermometers in a psychrometer change when the air temperature decreases if absolute humidity remains unchanged?

3) Why does dew appear in the evening after a hot day?

can lift a load that is 90% of the mass of the crane c) 90% of the electricity consumed by the engine goes to perform mechanical work d) 90% of the electricity consumed by the engine goes to heat the engine parts and the environment 2. In cold weather, a woolen sweater is warmer than in a nylon shirt, because... a) the thermal conductivity of wool is greater than nylon b) the thermal conductivity of wool is less than nylon c) wool releases more energy into the surrounding space than nylon d) wool absorbs more energy from the surrounding space than nylon 3. The readings of the dry and wet thermometers of the psychrometer are equal to 20 degrees. This means , that.. a) The psychrometer is broken b) relative air humidity 0% c) relative air humidity 20% d) relative air humidity 100% 4. When glass rubs against silk, the glass is charged positively, and when amber rubs against wool, the amber is charged negatively. This is explained by the fact that during the process of electrolysis.. a) glass loses electrons, and amber gains them; b) glass gains electrons, and amber loses them. c) glass loses protons, and amber gains them; d) glass gains protons, and amber loses them. 5. Two metal wires, one of which has plastic insulation and the other does not, are connected to the battery terminals. A magnetic field is around the wire. a) Occurs only in the first case b) Occurs only in the second case c) Occurs in both cases d) Occurs neither in the first nor in the second

Source: http://algebra.neznaka.ru/answer/823550_skolko-procentov-sostavlaet-otnositelnaa-vlaznost-vozduha-esli-pokazanie-suhogo-i-vlaznogo-termometrov-psihrometrov-sovpadaut-obasnite-otvet/

Problem solving lesson on the topic “Air Humidity”

Brainstorming Questions

1147. Why do fruits fog up when taken out of the refrigerator?

The temperature of the fruit is below the dew point - the temperature at which steam in the air becomes saturated and begins to condense on the surface of the fruit.

1148. Which is lighter: dry air with a volume of 1 m3 or humid air, also with a volume of 1 m3?

1149. Is the steam above the surface of eau de toilette in a closed bottle at a constant temperature saturating? Yes

1152. How will the relationship between the mass of the liquid and the mass of the saturating vapor change if the volume of the vessel is reduced at a constant temperature?

If the volume of the vessel is reduced at a constant temperature, then the mass of the liquid will increase, and the mass of the saturating steam will decrease, since the pressure of the saturating steam should remain the same. Therefore, some of the steam will condense.

1154. What is the absolute humidity of air that contains 100 g of moisture in a volume of 20 m3?

1155. Is the steam in the conditions of the previous problem saturated at a temperature of 0 0C?

1156. Based on the data in Table 10, determine whether the dependence of the density of saturating vapor in the air on temperature is linear.

1157. A volume of 1 m3 of air under normal conditions contains moisture weighing 2.41 g. What proportion and what percentage is this amount compared to the amount of moisture that the same air would contain in a volume of 1 m3 if the steam were saturated?

1158. What is the relative humidity of air saturated with water vapor?

1159. Why does heating air without additional evaporation lower its relative humidity?

1160. Under what condition does a decrease in the absolute humidity of atmospheric air lead to an increase in relative humidity?

1161. Using table 10, determine how much water in the form of steam is contained in the air of your classroom at a temperature of 20 0C and a relative humidity of 60%.

1162. A person feels comfortable at a relative humidity of 40-60%. Why can you feel a feeling of sweltering heat at an air temperature of 25 0C and a relative humidity of 80-90%, while at a temperature of 30 0C and a humidity of 30% you can feel good?

1164. In the evening, at an air temperature of 2 0C, the relative humidity is 60%. Will frost fall at night if the air temperature drops to -3 0C; up to -4 0С; to -5 0C?

1165. What is the relative humidity if the air temperature is 18 0C and its dew point is 10 0C?

1166. What percentage is the relative humidity of the air if the readings of the dry and wet thermometers of the psychrometer are the same?

1168. At an air temperature of 4 0C, the dry and wet thermometers of the psychrometer gave the same readings. What will the wet thermometer show if the air temperature rises to 16 0C? Assume that the water vapor pressure remains unchanged.

1. Do experiments.

b) Wrap the thermometer's mercury reservoir with cotton wool soaked in cologne and observe the thermometer readings. Blow on the cotton wool. Describe your observations.

c) If you breathe lightly on the mirror, it fogs up. Why?

2. Part of the rocket skin is sometimes made of a porous material, to which an easily evaporating liquid is supplied under pressure. Why does this prevent the case from overheating?

  • Pechurina Elena Petrovna
  • 63
  • 18.03.2018

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Air humidity

What is humidity?

Water evaporates from the surface of various bodies of water into the air. There is a lot of water vapor near bodies of water, so the air there is humid. There are no bodies of water in the desert, so the air there is dry.

What is absolute humidity?

Defined as the density of water vapor under given conditions. And density is equal to the ratio of mass to volume.

What is relative humidity?

Shows what percentage absolute humidity is of the amount of vapor that has a saturation state. Expressed as the ratio of absolute humidity to saturated humidity or as the partial pressure of a gas to saturated vapor pressure.

Partial pressure is the pressure of one individual gas from a mixture of gases. The total pressure of the entire mixture of gases is equal to the sum of all partial pressures.

Source: http://fizlite.ru/wet

44. Air humidity - V.I. Lukashik, Collection of problems in physics

Water vapor surrounding the cold fruit condenses on its surface.

Humid air is lighter.

Is because it is in dynamic equilibrium with eau de toilette.

From Table 10 we determine that the density is 0.6 kg/m3.

The water turned into saturated steam and returned the flask to its original shape under its pressure.

The mass of the liquid will increase due to a decrease in the mass of saturated vapor.

The vapor pressure will not change because it depends on temperature.

Saturated vapor pressure increases with temperature.

When the temperature drops.

Low humidity promotes the evaporation of moisture and cooling of the human skin and respiratory system.

Source: http://gdz-fizika.ru/7/vlazhnost-vozduha.html

Air humidity

1. Relative humidity

There are many open bodies of water on Earth, from the surface of which water evaporates: oceans and seas occupy about 80% of the Earth's surface. Therefore, there is always water vapor in the air.

It is lighter than air because the molar mass of water (18 * kg mol -1) is less than the molar mass of nitrogen and oxygen, of which air mainly consists. Therefore, water vapor rises. At the same time, it expands, since in the upper layers of the atmosphere the pressure is lower than at the surface of the Earth. This process can be approximately considered adiabatic, because during the time it occurs, the heat exchange of steam with the surrounding air does not have time to occur.

? 1. Explain why the steam cools.

As we will see later, when cooled to a certain temperature, which is called the dew point, water vapor begins to condense, collecting into tiny droplets of water. This is how clouds are formed.

They do not fall because they soar in rising air currents, just as hang gliders soar (Fig. 45.1). But when the drops in the clouds become too large, they begin to fall: it rains (Fig. 45.2).

The water vapor content of air is often characterized by the pressure it would exert if there were no other gases present. It is called the partial pressure of water vapor. (“Partial” means “partial” in Latin.)

We feel comfortable when the water vapor pressure at room temperature (20 ºC) is about 1.2 kPa.

? 2. What part (in percentage) is the indicated pressure of the saturated vapor pressure at the same temperature?

Clue. Use the table of saturated water vapor pressure values ​​at various temperatures. It was given in the previous paragraph. We provide a more detailed table here.

You have now found the relative humidity. Let's define it.

Relative air humidity φ is the ratio of the partial pressure p of water vapor to the pressure pn of saturated vapor at the same temperature, expressed as a percentage :

Comfortable conditions for humans correspond to relative humidity%. If the relative humidity is significantly lower, the air seems dry to us, and if it is higher, it appears humid. When relative humidity approaches 100%, the air is perceived as damp. In this case, the puddles do not dry out, because the processes of water evaporation and steam condensation compensate each other.

So, the relative humidity of the air is judged by how close the water vapor in the air is to saturation.

If air with unsaturated water vapor in it is compressed isothermally, both the air pressure and the unsaturated vapor pressure will increase. But the water vapor pressure will only increase until it becomes saturated!

As the volume decreases further, the air pressure will continue to increase, but the water vapor pressure will remain constant - it will remain equal to the saturated vapor pressure at a given temperature. Excess steam will condense, that is, turn into water.

? 3. The vessel under the piston contains air whose relative humidity is 50%. The initial volume under the piston is 6 liters, the air temperature is 20 ºС. The air begins to be compressed isothermally. Assume that the volume of water formed from steam can be neglected compared to the volume of air and steam.

a) What will be the relative humidity when the volume under the piston becomes 4 liters?

b) At what volume under the piston will the steam become saturated?

c) What is the initial mass of the steam?

d) By how many times will the mass of steam decrease when the volume under the piston becomes equal to 1 liter?

e) What mass of water will condense?

2. How does relative humidity depend on temperature?

Let's consider how the numerator and denominator in formula (1), which determines the relative humidity of the air, change with increasing temperature.

The numerator is the pressure of unsaturated water vapor. It is directly proportional to the absolute temperature (recall that water vapor is well described by the equation of state of an ideal gas).

? 4. By what percentage does the pressure of unsaturated vapor increase when the temperature increases from 0 ºС to 40 ºС?

Now let's see how the saturated vapor pressure in the denominator changes.

? 5. How many times does the saturated vapor pressure increase when the temperature increases from 0 ºС to 40 ºС?

The results of these tasks show that as the temperature increases, the saturated vapor pressure increases much faster than the unsaturated vapor pressure. Therefore, the relative air humidity determined by formula (1) quickly decreases with increasing temperature. Accordingly, as the temperature decreases, the relative humidity increases. We'll look at this in more detail below.

The equation of state of an ideal gas and the table above will help you in completing the next task.

? 6. At 20 ºС, the relative humidity was 100%. The air temperature increased to 40 ºС, but the mass of water vapor remained unchanged.

a) What was the initial pressure of water vapor?

b) What was the final pressure of water vapor?

c) What is the saturated vapor pressure at 40 ºС?

d) What is the relative humidity in the final state?

e) How will this air be perceived by a person: as dry or as wet?

? 7. On a damp autumn day, the temperature outside is 0 ºС. The room temperature is 20 ºС, relative humidity is 50%.

a) Where is the partial pressure of water vapor greater: in the room or outside?

b) In which direction will water vapor flow if you open the window - into the room or out of the room?

c) What would the relative humidity in the room become if the partial pressure of water vapor in the room became equal to the partial pressure of water vapor outside?

? 8. Wet objects are usually heavier than dry ones: for example, a wet dress is heavier than a dry one, and damp firewood is heavier than dry ones. This is explained by the fact that the weight of the moisture contained in it is also added to the body’s own weight. But with air the opposite is true: humid air is lighter than dry air! How to explain this?

3. Dew point

As the temperature decreases, the relative humidity of the air increases (although the mass of water vapor in the air does not change).

When relative humidity reaches 100%, water vapor becomes saturated. (Under special conditions, supersaturated steam can be obtained. It is used in cloud chambers to detect traces (tracks) of elementary particles in accelerators.) With a further decrease in temperature, condensation of water vapor begins: dew falls. Therefore, the temperature at which a given water vapor becomes saturated is called the dew point for that vapor.

? 9. Explain why dew (Fig. 45.3) usually falls in the early morning hours.

Let's consider an example of finding the dew point for air of a certain temperature with a given humidity. For this we need the following table.

? 10. A man with glasses entered the store from the street and discovered that his glasses were fogged up. We will assume that the temperature of the glass and the layer of air adjacent to it is equal to the air temperature outside. The air temperature in the store is 20 ºС, relative humidity 60%.

a) Is the water vapor in the layer of air adjacent to the glasses saturated?

b) What is the partial pressure of water vapor in the store?

c) At what temperature is the pressure of water vapor equal to the pressure of saturated vapor?

d) What could be the air temperature outside?

? 11. A transparent cylinder under the piston contains air with a relative humidity of 21%. The initial air temperature is 60 ºС.

a) To what temperature must the air be cooled at a constant volume in order for dew to form in the cylinder?

b) How many times must the volume of air be reduced at a constant temperature for dew to form in the cylinder?

c) The air is first compressed isothermally and then cooled at constant volume. Dew began to fall when the air temperature dropped to 20 ºC. How many times was the volume of air reduced compared to the initial volume?

? 12. Why is extreme heat more difficult to tolerate when humidity is high?

4. Humidity measurement

Air humidity is often measured with a psychrometer (Fig. 45.4). (From the Greek "psychros" - cold. This name is due to the fact that the readings of a wet thermometer are lower than those of a dry thermometer.) It consists of a dry and wet thermometer.

Wet bulb readings are lower than dry bulb readings because the liquid cools as it evaporates. The lower the relative humidity, the more intense the evaporation.

? 13. Which thermometer is located to the left in Figure 45.4?

So, according to the readings of thermometers, you can determine the relative humidity of the air. To do this, use a psychrometric table, which is often placed on the psychrometer itself.

To determine the relative humidity of the air, you need to:

– take thermometer readings (in this case 33 ºС and 23 ºС);

– find in the table a row corresponding to the dry thermometer readings and a column corresponding to the difference in thermometer readings (Fig. 45.5);

– at the intersection of the row and column, read the relative air humidity value.

? 14. Using the psychrometric table (Fig. 45.5), determine at what thermometer readings the relative air humidity is 50%.

Additional questions and tasks

15. In a greenhouse with a volume of 100 m3, the relative humidity must be maintained at least 60%. Early in the morning, at a temperature of 15 ºС, dew fell in the greenhouse. The temperature in the greenhouse during the day rose to 30 ºС.

a) What is the partial pressure of water vapor in a greenhouse at 15 ºС?

b) What is the mass of water vapor in the greenhouse at this temperature?

c) What is the minimum allowable partial pressure of water vapor in a greenhouse at 30 ºC?

d) What is the mass of water vapor in the greenhouse?

e) What mass of water must be evaporated in the greenhouse in order to maintain the required relative humidity in it?

16. On a psychrometer, both thermometers show the same temperature. What is the relative humidity? Explain your answer.

Source: http://phscs.ru/physics102/humidity

What percentage is relative humidity?

Moisture is one of the essential components of all living organisms on earth, the biosphere that surrounds us, as well as most materials used by humans. There is almost always some amount of water vapor in the air around us.

The moisture content in the environment influences the nature and intensity of biochemical and physicochemical processes occurring in living objects. The physical, chemical, mechanical and technological properties of a significant part of non-metallic materials depend on humidity. Almost all industries, agriculture, energy and construction use drying and humidification processes to change the moisture content of materials.

Air humidity plays a huge role in the world and human daily life. People’s health, the climate on the planet, the quality of furniture, books, and buildings depend on it.

The humidity of the air depends on the amount of water vapor contained in it.

Relative air humidity is of great importance, messages about which are heard every day in weather forecast reports.

Relative humidity is the ratio of the density of water vapor contained in the air to the density of saturated vapor at a given temperature, expressed as a percentage.

The value ρ is called absolute humidity. Its density of water vapor in the air, or its pressure Pa. If the temperature is low, then a given amount of water vapor in the air may be close to saturation, the air will be damp. At a higher temperature, the same amount of water vapor is far from saturation, the air is dry. To judge the degree of humidity, it is important to know whether the water vapor in the air is close or far from the saturation state. For this, the concept of relative humidity is introduced - because it gives a clearer idea of ​​​​the degree of air humidity. Relative air humidity is measured by a number indicating what percentage the absolute humidity is of the water vapor pressure ρ us saturating the air at its existing temperature.

If moist air is cooled, then the steam in it can be brought to saturation, and then it will condense.

Examples: dew falling in the morning, fogging up of cold glass if you breathe on it, the formation of a drop of water on a cold water pipe, dampness in the basements of houses.

To measure air humidity, measuring instruments are used - hygrometers.

Since it is difficult to directly measure water vapor pressure in the air, relative humidity is measured indirectly.

The principle of operation of a hair hygrometer is based on the property of defatted hair (human or animal) to change its length depending on the humidity of the air in which it is located.

It is tightly stretched over a metal frame. The change in hair length is transmitted to the arrow moving along the scale. In winter, a hair hygrometer is the main instrument for measuring outdoor air humidity.

A more accurate hygrometer is a psychrometric hygrometer - psychrometer (in other Greek “psychros” means cold).

It is known that the rate of evaporation depends on the relative humidity of the air.

The lower the air humidity, the easier it is for moisture to evaporate.

A psychrometer has two thermometers. One is ordinary, it is called dry. It measures the ambient air temperature. The bulb of another thermometer is wrapped in a fabric wick and placed in a container of water. The second thermometer does not show the air temperature, but the temperature of the wet wick, hence the name wet thermometer. The lower the air humidity, the more intensely the moisture evaporates from the wick, the greater the amount of heat per unit time is removed from the moistened thermometer, the lower its readings, therefore, the greater the difference in the readings of the dry and moistened thermometers.

Having determined the difference between the readings of dry and humidified thermometers, the value of relative humidity is found using a special table located on the psychrometer.

Both excessive dry air and high humidity are harmful to human health.

The most comfortable air humidity for humans lies in the range of 40-60%.

High temperatures are easier to tolerate in dry air. The heat in a dry desert may not be as debilitating as 25 degrees after heavy rain, when the air humidity is very high. In order not to overheat, the body needs to sweat a lot in the heat. However, with high humidity, sweat will not dry out and will not cool the body.

At high air temperatures and low humidity, a person sweats and removes moisture from the body mainly through the skin, and not through the kidneys. This property of the body is used in medicine for kidney diseases.

English aeronauts, rising over London during fog, observed the following curious phenomena. During the rise of the ball, nothing was visible in the fog and all sounds coming from the ground were greatly weakened, making them seem very distant. Immediately after rising above the layer of ground fog, all the sounds of the city were again clearly audible. Due to the lack of perspective when viewing the surrounding space and the rather strong absorption of sound in the clouds, the aeronauts felt isolated from the ground. Only occasionally it was disturbed by faint sounds of the earth: train whistles, roosters crowing, dogs barking. Identification of earthly sounds was made difficult due to changes in their timbre as a result of preferential absorption of high frequencies in the clouds.

In the practice of navigation, there are cases when sound signals in fog are heard at long distances and at the same time inaudible at closer ones. If the sound beacon and the ship are not in the fog zone at the same time, then, depending on the angle of incidence of the sound rays on the boundary of clear air and fog, both strong absorption of the signal and the formation of an echo are possible.

What is easier: dry air with a volume of 1 m 3 or humid air, also with a volume of 1 m 3?

Is the steam above the surface of eau de toilette saturating in a closed bottle at a constant temperature?

A tourist returned a dented metal flask to its original shape after he partially filled the flask with water, closed it tightly and held it over a fire. Explain why.

What is the relative humidity of air saturated with water vapor?

The wet thermometer of the psychrometer shows a temperature of 10 °C, and the dry thermometer shows 14 °C. Find the relative humidity.

What percentage is the relative humidity of the air if the readings of the dry and wet thermometers of the psychrometer are the same?

A person feels comfortable at a relative humidity of 40-60%. Why can you feel a feeling of sweltering heat at an air temperature of 25 ° C and a relative humidity of 80-90%, while at a temperature of 30 ° C and a humidity of 30% you can feel good?

***Using the table, determine how much water in the form of steam is contained in the air of your room at a temperature of 20 ° C and a relative humidity of 60%. Calculate the volume of the room yourself.

Saturated water vapor density

Difference between dry and wet thermometer readings, °C

Source: http://veciy.ru/24283

Humidity

In this article, we will consider problems of a mixed type: here we will need absolute humidity, relative humidity, heat balance, and even Newton’s veiled second law.

Problem 1. The pressure of saturated water vapor at temperature C is 44.6 mmHg. Art. What is the mass at this temperature of 1 m of moist air at a relative humidity of 80% and a pressure of 1 atm?

The vapor pressure at a given relative humidity will be . Knowing this, we can determine the mass of steam using the Mendeleev-Clapeyron equation:

Let's convert the pressure from mmHg. to Pascal: .

Then the mass of steam is:

But we only calculated the mass of the steam, but air also has weight. Let's determine its mass using the same equation:

Sum of masses of steam and air:

Answer: mass of moist air 1.163 kg

Problem 2. A vessel with a volume of 100 liters at C contains air with a relative humidity of 30%. What will be the relative humidity of the air in a vessel if 1 g of water is introduced into it and evaporated at this temperature?

At this temperature, the density of saturated vapor is g/m. Then at a relative humidity of 30% the vapor density will be

In other words, every cubic meter of such air under such conditions contains 9.12 g of water. But we have not a meter, but only 100 liters of air, therefore, in this volume, which is less than 1 m 10 times, there will be 10 times less water: 0.912 g. Let us now determine the new relative humidity of the air if we evaporate another 1 g water:

Problem 3. The relative humidity of the air filling a vessel with a volume of 0.7 m at C is 60%. How much water must be evaporated into this volume to completely saturate the steam, if the temperature remains constant?

At this temperature, the density of saturated vapor is 21.7 g/m. If we have a relative humidity of 60%, then the actual vapor density is

Thus, each meter contains 13 g of water. And if the steam were saturated, it would contain 21.7 g - that is, each cubic meter is not enough to saturate a g of water. But we have not a meter, but 0.7 - therefore, there is not enough g to reach saturation.

Problem 4. A sealed tube with a volume of 0.4 liter contains water vapor under a pressure of 60 mmHg. at a temperature of C. How much dew will fall on the walls of the tube when it is cooled to C?

According to the Mendeleev-Clapeyron equation

Saturated vapor pressure at temperature – mmHg, then the mass of steam

Then it will fall out in the form of dew

Answer: 8.6 mg of water will fall as dew.

Problem 5. Under a light piston in a cylinder with a cross-section m there is 1 kg of water at a temperature C. A piece of hot iron weighing 1 kg is lowered into the water. To what temperature was the iron heated if the piston then rose to a height of 0.64 m? Atmospheric pressure is normal, heat transfer and heat capacity of the cylinder are neglected.

Let's analyze what happened after the iron was lowered. The iron cooled, the water heated up. The water boiled and partially evaporated. It is important that it is partial: then, since not all of it has evaporated, then the temperature of the steam cannot be more than C. The steam pressure increased, and it raised the piston. The volume it occupied is m. The steam pressure is equal to atmospheric pressure: the steam pressure counteracted the external pressure. Then the mass of water that turned into steam is:

Let's create a heat balance equation.

Answer: the initial temperature of iron is .

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All site materials are free! When copying, please put a link to the “Simple Physics” website.

Source: http://easy-physics.ru/vlazhnost/

What percentage is relative humidity?

Water is one of the essential components of all living organisms on earth, the biosphere that surrounds us, as well as most materials used by humans. The moisture content in the environment influences the nature and intensity of biochemical and physicochemical processes occurring in living objects. The physical, chemical, mechanical and technological properties of a significant part of non-metallic materials depend on humidity. Almost all industries, agriculture, energy and construction use drying and humidification processes to change the moisture content of materials.

For the first time I learned about air humidity in physics lessons, studying the topic “Thermal Phenomena”. The entertaining experiments and laboratory work made a huge impression on me, and I wanted to learn even more about this amazing phenomenon. Air humidity plays a huge role in the world and human daily life. People’s health, the climate on the planet, the quality of furniture, books, and buildings depend on it. I would really like people to know as much as possible about the dependence of health on humidity, how we can take care of our planet, preserve ancient books and museums.

Study air humidity.

Investigate changes in humidity in the Earth's atmosphere.

To study the influence of air humidity on humans, to introduce natural and artificial “meters” of humidity.

Investigate the destructive effect of humidity on paper.

The tasks that I set for myself:

collection of material on the topic of the essay and its processing;

building the content of the main part;

conclusions about the work done;

design of generalized material;

presentation of the abstract at the scientific and practical conference of students at school No. 102.

Hypothesis: air humidity is an important factor in the life of a living organism.

Methods: theoretical analysis of literature, practical method.

My work consists of 7 chapters. I have studied and processed the following materials: literary sources, including educational, scientific, periodicals and Internet sites. Applications have been prepared that contain: a table of changes in humidity in the earth's atmosphere, a table of hydrological cycles, a hair hygrometer, a psychrometer, an example of a psychrometric table, the location of vessels and capillaries in wood.

1. Humidity and water

1.1 Humidity characteristics

An important characteristic of the state of the atmosphere is air humidity or the degree of saturation of the air with water vapor. It is expressed by the ratio of the content of water vapor in the air to its content when the air is saturated at a given temperature. To quantify air humidity, absolute and relative air humidity are used.

Absolute air humidity is measured by the density of water vapor in the air, or its pressure Pa. If the temperature is low, then a given amount of water vapor in the air may be close to saturation, the air will be damp. At a higher temperature, the same amount of water vapor is far from saturation, the air is dry. To judge the degree of humidity, it is important to know whether the water vapor in the air is close or far from the saturation state. For this, the concept of relative humidity is introduced - because it gives a clearer idea of ​​​​the degree of air humidity. Relative air humidity is measured by a number indicating what percentage the absolute humidity is of the water vapor pressure PH saturating the air at its existing temperature.

The temperature at which the air becomes saturated with water vapor during its cooling process is called the dew point. When the air is saturated with water vapor, the water in it no longer evaporates. With increased humidity, a person feels low temperatures more acutely. Many could see that severe frosts with low air humidity are more easily tolerated than less severe frosts with high humidity. The fact is that water vapor, like liquid water, has a much greater heat capacity than air. Therefore, in humid air the body gives off more heat to the surrounding space than in dry air. In hot weather, high humidity again causes discomfort. Under these conditions, the evaporation of moisture from the surface of the body decreases (a person sweats), which means that the body cools less well and, therefore, overheats. In very dry air, the body loses too much moisture and, if it is not possible to replenish it, this affects a person’s well-being. [2] There is practically no such thing as absolutely dry air. It always contains moisture at least in trace quantities. It turns out that tiny amounts of water can sometimes have a dramatic effect on the chemical properties of many substances. In 1913, the English chemist Baker found that liquids dried for nine years in sealed ampoules boil at much higher temperatures than indicated in reference books. For example, benzene begins to boil at a temperature 26° higher than usual, and ethyl alcohol - at 60, bromine - at 59, and mercury - almost 100°. The freezing point of these liquids has increased. The influence of traces of water on these physical characteristics has not yet been satisfactorily explained. In well-dried oxygen, coal, sulfur, and phosphorus burn at a temperature much higher than their combustion temperature in undrained air. Moisture is believed to play a catalytic role in these chemical reactions. Fog is formed from air supersaturated with water vapor. It consists of tiny droplets of water ranging in size from 0.0001 to 0.1 mm. Water droplets condense more easily on solid particles in the air in the form of dust. The processes of artificial rain formation are based on this principle. To do this, seeds are introduced into the clouds, on which water condenses or ice crystallizes. Large hailstones are produced when crystallization occurs at a small number of centers. If a lot of seeds are introduced into the cloud, you will get small ice crystals (they cannot grow, since all the water will be crystallized), which, when falling to the ground, often have time to melt and turn into rain. For widespread use, these salts are quite expensive. However, hail can cause much greater economic losses. In addition to rain and hail, precipitation also falls in the form of snow. [1]

2. Air humidity in different parts of the globe

2.1 Changes in humidity in the Earth's atmosphere

The air humidity in the earth's atmosphere varies widely. Thus, near the earth's surface, the content of water vapor in the air averages from 0.2% by volume in high latitudes to 2.5% in the tropics. Accordingly, vapor pressure in polar latitudes in winter is less than 1 Mb (sometimes only hundredths of Mb) and in summer below 5 Mb; in the tropics it increases to 30 MB, and sometimes more. In subtropical deserts, e is reduced to 5-10 Mb (1 Mb = n/m2). Relative humidity r is very high in the equatorial zone (the annual average is up to 85% or more), as well as in the polar latitudes and in winter inside the mid-latitude continents - here due to the low air temperature. Monsoon regions (India) are characterized by high relative humidity in summer. Low values ​​of r are observed in subtropical and tropical deserts and in winter in monsoon regions (up to 50% and below). With altitude, relative humidity and the acceleration of gravity decrease rapidly. At an altitude of 1.5-2 km, vapor pressure is on average half that of the earth's surface. The troposphere (lower layers) accounts for 99% of the atmospheric water vapor. On average, the air above each m2 of the earth's surface contains about 28.5 kg of water vapor. (Appendix 1) [4]

2.2 Daily and annual fluctuations in humidity

The daily variation of vapor pressure over the sea and in coastal areas is parallel to the daily variation of air temperature: moisture content increases during the day with increasing evaporation. The diurnal cycle is the same in the central regions of the continents during the cold season. A more complex diurnal cycle with two maxima - in the morning and in the evening - is observed in the interior of the continents in the summer. The daily variation of relative humidity is the opposite of the daily variation of temperature: during the day, with increasing temperature and, consequently, with increasing saturation elasticity E, relative humidity decreases. The annual variation of vapor pressure is parallel to the annual variation of air temperature; Relative humidity varies annually inversely to temperature. [4]

When water evaporates, its molecules form a water gas called water vapor. The atmosphere also contains liquid water in the form of cloud droplets and raindrops. Ice crystals, snowflakes and hailstones are atmospheric water in a frozen state. Unlike most other gases present in the atmosphere, the content of water vapor can vary greatly. It depends on the air temperature and the state of the evaporating surface (water, wet or dry soil, ice). In very cold and therefore dry air, water vapor can only be present in small quantities that are difficult to measure; in hot air its content can reach 4 percent of the air volume and then such air becomes humid.

When water vapor enters the air, it, like all other gases, creates a certain pressure called partial pressure. It is expressed in units of pressure (hPa). As water molecules move into the air, the vapor pressure in the air increases. When equilibrium is achieved between the number of molecules leaving the water and returning to it, the steam becomes saturated and its pressure is equilibrium. If the air temperature continues to increase, then to maintain a saturated state of steam, the number of molecules entering the air must also increase, if, of course, there is still liquid. Vapor pressure is a measure of another quantity, also expressing the amount of steam contained in the air, called absolute humidity. Absolute humidity is the mass of water vapor contained in a unit volume of air. It is usually expressed in g/m3.

The amount of water vapor in the air is often expressed in units of relative humidity, the value of which is reported in daily weather reports. It represents the ratio of the amount of steam actually contained in the air to the amount of saturated steam at a given temperature and is expressed in %. This value is easy to explain with the help of real-life examples. When the air is saturated, its relative humidity is 100%; we can say that saturated air is filled with water vapor, and if it is 10%, then the vapor in the air is 10% of the maximum possible. Therefore, if the relative humidity is low, say 10%, then wet laundry outside will dry quickly, especially on a hot day.[16]

It is well known that a temperature of +30°C is more easily tolerated by a person in a dry climate than in a humid climate. When relative humidity is low, sweat from the surface of the body quickly evaporates, which brings a feeling of coolness. Water vapor enters the atmosphere as a result of the evaporation of water from oceans and lakes, from the surface of the earth, and as a result of transpiration (evaporation of water by plants). 5.05·10 8 Mt of water evaporates annually from the surface of the oceans, and 0.72·10 8 Mt of water evaporates from the surface of the continents. Water vapor is transported by atmospheric movements, condenses and returns to the earth's surface in the form of rain and snow. Most of the returned water evaporates again; the rest is absorbed into the ground, ends up in streams and rivers and flows to lakes and oceans, and then evaporates from their surface. This course of events is called the hydrological cycle. The total amount of water involved in the hydrological cycle is thousands. km 3, which can be expressed as a layer of water 25 mm thick, uniformly covering the entire globe. As can be seen from Table 2 (Appendix 2), precipitation and evaporation for the earth as a whole amount to 1130 mm per year. Precipitation over land (800 mm) is greater than evaporation (485 mm) and their difference is equal to the annual flow of rivers into the ocean (315 mm). Over the ocean, on the contrary, more water evaporates (1400 mm) than precipitation falls (1270 mm), and this difference represents the flow of water vapor from the ocean to land. In a long-term withdrawal, the amount of water participating in the moisture cycle remains constant. Thus, there is 40 times more precipitation on Earth per year than there is water vapor in the atmosphere.

On average, 45 hydrological cycles are observed on Earth per year, and water vapor in the atmosphere is renewed every 8-10 days. This lifetime of water vapor is much shorter than the lifetime of many other gases in the atmosphere. For example, the lifetime of carbon dioxide in the atmosphere is several decades, oxygen - about 3000 years.[4]

Despite its relatively short lifetime, water vapor is transported over vast distances from the place of evaporation to the place of precipitation. The speed of water vapor transfer by air currents along latitude (zonal transfer) averages 220 km/day. In this case, the average number of changes of water vapor per revolution around the Earth is 13.5. During the year, 3 km of water falls from the atmosphere in the form of various precipitation. Evaporating such a quantity of water requires a lot of heat. For the entire earth's surface this amounts to J/year, i.e. 25% of solar energy reaching the Earth. When water vapor condenses in the atmosphere, this heat is returned to the atmosphere, what is said to be the latent heat of condensation. In atmospheric processes, water vapor and its condensation products largely determine weather conditions, not only due to the development of cloudiness and precipitation, but also by participating in energy processes. [12]

3. The influence of air humidity on human life.

3.1 Diseases, skin aging

Humidity is one of the most important air parameters that directly affects human health. The optimal humidity level at which a person feels most comfortable is 60-70%.

Meanwhile, in summer in dry weather it rarely exceeds 40%, and in winter it drops to 25-30%. After all, cold air contains little moisture, so when we ventilate a room in winter, the air in it becomes drier. Lack of moisture leads to dryness and early aging of the skin, irritation of the mucous membrane, which opens the way for infections and increases the likelihood of various respiratory diseases. Here lies the reason for the appearance of wrinkles. Cosmetic campaigns advertise super moisturizing creams and miracle gels with might and main. This is understandable - it is much more profitable to fight the effect than the cause. Meanwhile, women living in climates with normal moisture content have skin that remains smooth and elastic even in old age, which cannot be said about citizens living in dry climates. The humidity regime is especially important for small and infant children, because in the first months and years of life they have very delicate and sensitive skin, mucous membranes of the mouth and nose. Therefore, the humidity in the room where the newborn sleeps should be at least 50%. Dry air is generally dustier, because tiny dust hangs in it, which is normally “bound” by humidity.

Our body is 90% water. Therefore, maintaining optimal relative air humidity for a person is not just comfort, it is a vital need and a guarantee of health. In dry conditions, people become drowsy and distracted, fatigue increases, general well-being worsens, and performance and immunity decrease. In a room with dry air, the likelihood of contracting a respiratory infection increases. Children and people with respiratory diseases, asthmatics and allergy sufferers primarily suffer from a lack of humidity. In addition, it is known that dry air contains an excess amount of positively charged ions, which in turn contributes to the development of such a common disease as stress. Human skin is 70% water. As a result of metabolic processes, it loses about half a liter of moisture during the day, and in winter - up to a liter. After all, it is enough to increase the air humidity in the apartment, and moisture loss will be significantly reduced. [10]

Dry air is one of the main causes of allergies. Allergens (causative agents of allergic reactions) actively spread in it. In addition, it leads to a weakening of the human immune system. What is an allergy? Allergy is an increased sensitivity to various substances, manifested in the form of unusual reactions upon contact with them. Manifestations of allergies are very different. There may be painful and repeated attacks of sneezing with profuse watery discharge from the nose, nasal congestion, itching of the eyelids and lacrimation, pain in the eyes, itching of the mucous membranes of the nasopharynx, widespread skin itching. Sometimes an allergic reaction develops rapidly and can result in anaphylactic shock. According to statistics, every fifth inhabitant of our planet suffers from allergies. In Russia, this disease affects from 5% to 30% of the population (depending on the region). There are several types of allergens: - household: house and library dust, house dust mites; - epidermal: hair and desquamated epidermis (dander) of animals, bird feathers, dry fish food; - pollen: pollen of trees, shrubs, grasses; - food: Food. [10]

Indoor flowers and plants suffer the most from a lack of air humidity. Drooping greenery and buds, yellowed and wrinkled tips of leaves, “leaf fall” at the wrong time - all this indicates low air humidity in the room.

How much water does a flower need? This is difficult to answer. If for open ground plants the rules of watering are more or less similar, then among indoor flowers it is necessary to distinguish at least four groups that differ sharply from each other in their love of moisture: desert plants, plants of dry subtropics, plants of humid subtropics and plants

tropical rainforests. The identification of these groups is necessary not only for the correct selection of watering regimes, but also in order to determine the necessary heat and light conditions and correctly place flowers in the room. Knowing the peculiarities of the natural climatic conditions for a given type of plant, we should strive to recreate them in the rooms or, if this is impossible, even refuse to grow some flowers. Climate is a multifactorial phenomenon. What is a microclimate (in this floriculture context), if not an artificially created climate for a plant in a local area of ​​space? Humidity, temperature and light are part of a single complex of climatic factors. Let's consider brief characteristics of climatic zones.

Deserts: Only a few plants can live and develop in desert conditions, but these few are so adapted to the climate there that nothing else will suit them. Even the metabolism of the majority of desert inhabitants is structured completely differently than that of all other representatives of the plant kingdom, so they cannot even be “retrained” by acclimatization. In ordinary plants, photosynthesis occurs during the day; in many succulents, on the contrary, carbon dioxide is absorbed only at night, and during the day the stomata are closed to prevent the evaporation of moisture from the body. The most striking and characteristic feature of the desert is low humidity. Under natural conditions, less than 20 cm of precipitation falls per year there, and sometimes even less: in the Atacama Desert (coast of Peru and northern Chile), the average annual amount rarely exceeds 2 cm! For comparison: in temperate climates there are from 75 to 250 cm, in the humid tropics - from 200 to 400 cm, in tropical rain forests there are even more: up to 2000 cm per year. Consequently, compared to some other houseplants, desert natives sometimes need two hundred times less moisture. In addition to the required total amount of water, one must also remember the peculiarity of its supply regime: in deserts, precipitation falls unevenly across seasons, and therefore herbaceous species are characterized by a sharp seasonal change in vegetation activity (that is, one or two periods of intensive growth and, accordingly, periods of deep dormancy.

Subtropics: Dry and humid subtropics (annual precipitation averages 150 mm) have high atmospheric and soil moisture. It is not constant and changes with the seasons, from heavy rains to drought. The temperature is quite high, its daily fluctuations are much less pronounced than in deserts. In the humid subtropics there are a lot of forests and most terrestrial plants are shade-tolerant. Tropics: The tropics are located in equatorial and subequatorial latitudes. There is a lot of moisture in the tropics, both soil and atmospheric, and therefore the “natives” of this zone are, of course, moisture-loving. Despite the presence of seasonal fluctuations, there are practically no drought-resistant or cold-resistant forms among indoor plants. The rest period in the vast majority of tropical species is very weak. Let's consider the features of watering indoor plants. Having divided plants by origin from different climatic zones, we will immediately know the approximate need of these plants for water, but it does not at all follow that moisture-loving flowers can be uncontrollably filled with huge amounts of water, and xerophytes and succulents can be completely dried out, just like plants that are in a dormant period. You need to know two restrictions for watering: the ground should not be too wet (for moisture-loving species), and the earth ball should never dry out completely (for drought-resistant and dormant plants). Only cacti can be watered when the soil is completely dry.[8]

4.2 Artificial meters

“Air humidifiers” are devices that allow you to maintain a comfortable level of indoor air humidity without significant energy consumption. The basis of the action of most of them is associated with the use of evaporators operating on the principle of “cold” or “hot” evaporation of moisture. In addition to humidifying the air, they can flavor it to suit your taste. In addition, they are all easy to use and reliable in operation. Creating comfortable conditions in our habitats is the key to our health. Unfortunately, the problem of maintaining the required level of humidity in living and working spaces has never been taken seriously. Meanwhile, in winter and summer, during the operation of central heating or air conditioning, the air contains too little moisture, both for the normal well-being of a person, and for most indoor plants, and even for the safety of wooden furniture.

Traditional humidifiers work on the principle of “cold” evaporation. The special evaporator mesh is completely saturated with moisture. The built-in fan sucks in dry air from the room and drives it through a wet mesh, which ensures optimal air humidification and does not require additional control devices.

Steam humidifiers use the principle of “hot” evaporation in their operation. Using two electrodes, water is heated and turned into steam. They are characterized by high productivity, and for their most economical operation it is recommended to regulate the humidification speed using controllers.

Ultrasonic humidifiers use more efficient air humidification technology. It allows, through high-frequency vibrations, to transform water into a microscopic “water cloud”. Using a fan, dry air is sucked in, passes through the “water cloud” and is then distributed throughout the room. A highly efficient filter cartridge removes minerals and impurities from water before it is converted. A distinctive feature of these humidifiers is their very low noise level.

The hair hygrometer is designed to measure the relative humidity of the air. The operation of the device is based on the property of defatted human hair to change its length depending on changes in the relative humidity of the surrounding air. The main purpose of a hair hygrometer is to measure humidity in frosty weather, when humidity cannot be determined by a psychrometer. But since readings from a hygrometer require corrections obtained from comparison with a psychrometer, to derive these corrections, observations from the hygrometer are carried out throughout the year. If, during the countdown, it turns out that the end of the arrow has gone beyond the hundredth division, then you need to estimate by eye what division the arrow would have been on if the scale had been extended to 110.

Hair hygrometer device:

1-skimmed hair, 2-adjusting screw, 3-shackle, 4-lever, 5-arrow,

6-scale (Appendix 3). During my physics elective, the kids and I had the pleasure of making this device.[13]

The device consists of two identical thermometers (Appendix 4). The reservoir of one of the thermometers is wrapped in a piece of clean cambric, the lower edge of which is lowered into a small glass cup with distilled water. Water wets the cambric and evaporates on the thermometer ball if the water vapor in the air is not saturated. Due to the loss of heat through evaporation, the bulb of the thermometer cools and the wetted thermometer shows a lower temperature than the dry thermometer. The greater the difference between the pressure of water vapor contained in the air and the pressure of saturated vapor, the greater the difference between the readings of thermometers. Based on the readings of dry and wet thermometers, using special psychrometric tables, the water vapor pressure and relative air humidity are found (Appendix 5).[3]

5. Destructive effects of humidity

The weather is not only the topic of many idle conversations, but it also often determines our behavior. Depending on the weather, we decide whether to go on a picnic, go to the skating rink, go boating, go swimming or skiing. The climate can be used to judge what kind of clothes people wear, what they eat, and in what kind of housing they live. Depending on the weather, holidays can be very good or bad. Weather affects the health, well-being and well-being of the entire population.

The Earth's climate is changing not only due to global warming, but also due to increased air humidity. American and British scientists came to this conclusion. In less than the last 30 years, the level of air humidity near the earth's surface has increased by 2.2%, they note. This figure has also increased significantly over the surface of the World Ocean. Heat and high humidity levels have an even greater negative impact on people, experts emphasize. This is expressed, first of all, in the fact that at higher humidity, the heat exchange of the human body significantly worsens. Scientists have also found that rising humidity levels, like greenhouse gases, are the result of human activity. Moreover, according to researchers, if the international community does not take any action, the environmental situation on our planet will only worsen. Thus, with general climate warming of 1 degree Celsius, humidity will increase by 6%. Using temperature forecasts from the International Commission on Climate Change, scientists have found that by 2100, the planet's humidity will increase by 24%.[7]

The oldest library in Simferopol may “die”. Local authorities refuse to allocate funds not only for the purchase of new books and periodicals, but also for the renovation of one of the oldest libraries in Crimea, which has existed for 101 years. Along with the library, rare books also perish. The library building was built at the end of the 19th century. Now it is in disrepair. No renovations have been done here for more than 30 years. The walls were damp. The plaster is falling off. High humidity destroys books, for example, the publication of Zhukovsky’s works in 1902. This year, only 5 thousand UAH were allocated to the library. for purchasing books. There is no money for the rest. More than 3 thousand readers come to the library every year, but the authorities continue to ignore the problems of the century-old library. Its workers say, not without bitterness, that Simferopol may lose not only unique funds, but also a historical building.[9]

5.3 Humidity and servers

At the moment, humidity is the most underestimated in terms of importance of the server room life support parameter. A few simple facts: - When the humidity is below 30%, air flow through the server causes static electricity to build up on the chips and circuit boards inside the server. Sometimes a sufficiently large voltage accumulates to cause breakdowns, for example, between the legs of adjacent microcircuits. This leads to failures, which are traditionally attributed to one or another software company. If we take air with a temperature of -7.5 degrees Celsius and a relative humidity of 100% and heat this air to +25 degrees without adding moisture, then the relative humidity of this air will become. 10%!

What conclusions can be drawn? 1. In the server room, it is necessary to at least constantly monitor the humidity. If the humidity is below 35% (since most humidity sensors have an error of +/-5% rH), it is necessary to use grounding bracelets in the server room. Ideally, you need to maintain the humidity in the server room at 40-55%. 2. Under no circumstances should any forced ventilation be installed in the server room. Exhaust ventilation should provide the minimum level of air exchange acceptable for server rooms.[14]

6.1 Vessels and capillaries in wood

The properties of wood are very dependent on the moisture content. The absolute moisture content of wood is the ratio of the mass of moisture contained in a given volume of wood to the mass of absolutely dry wood, expressed as a percentage. Relative humidity of wood is the ratio of the mass of moisture contained in wood to the mass of wood in a wet state, expressed as a percentage. First of all, free moisture evaporates from the wood; with further drying, the process of evaporation of bound moisture begins, as a result of which a significant change in the physical and mechanical properties of the wood occurs. A living (freshly cut) tree will typically have a moisture content in the region of 50% -100%. After cutting, the moisture content decreases. First, free moisture evaporates until the so-called saturation point of the fiber is reached. This is the point at which all free water has gone and the remaining moisture is bound inside the cell walls. This point depends on temperature, but for most types of wood it is 30% (based on dry weight). When bound moisture is removed from wood, the linear dimensions and volume of wood decrease. This process is called drying. Shrinkage usually depends on the density of the wood, with hardwoods exhibiting greater shrinkage than softwoods.[5]

One of the lightest woods is balsa, or ochrome. The specific gravity of wood is 0.12, that is, a cubic decimeter weighs only 120 grams, it is almost two times lighter than cork, 7 times lighter than the wood of ordinary trees and 9 times lighter than water. However, balsa wood acquires such properties after drying.

In a living tree, the wood consists of large cellulose cells filled with cell sap, and the trunk of a freshly cut tree is very heavy. To prevent the log from rotting, it is placed vertically or dried in special dryers (it can rot in two days if left on the ground). Dry wood acquires high strength (close to the strength of oak), but it is soft and spongy and does not have growth rings, since the tree grows continuously.

The unique properties of balsa wood were known to the Incas, who hollowed out canoes from it and made rafts on which they made long trips. When the Spaniards saw these wonderful rafts, they were amazed, but they did not know the material from which they were made, they gave it the name “balsa” or “balsa”, which means “raft” in Spanish.

Over time, balsa wood acquired important economic importance. It is used in construction and especially aircraft construction, for finishing work. To give it a beautiful appearance, it is pre-veneered, that is, covered with plywood made from valuable tree species. In this case, the products weigh twice as much as spruce wood, but are not particularly strong.

The great sponginess of balsa wood makes it an excellent thermal, noise and vibration insulating material. The following experiment was carried out: a piece of frozen butter was placed in a thick-walled balsa box and kept in it for 8 days at an air temperature of plus 28 ° C. The butter did not melt. That’s why the interior walls of refrigerators are lined with balsa boards. Balsa pillows are placed under heavy vibrating machines. Interestingly, a person can easily hold a balsa log 4.5 meters long and 50 centimeters in diameter on his shoulders without much difficulty.

Let us recall that the famous Norwegian explorer Thor Heyerdahl made his raft “Kon-Tiki” from 9 balsa logs, fastened with rope, and sailed on it across the Pacific Ocean - from the shores of Peru to Polynesia.

Balsa grows from Mexico to Bolivia and is cultivated in India, Venezuela, and Costa Rica. This is an unusually fast-growing tree, by 7 years it reaches a height of 22 meters and a diameter of 60 centimeters, and by 10 years it reaches 30 and 1 meter, respectively. In favorable conditions, it grows 4 meters per year. A freshly cut balsa tree can have a humidity level of up to 600% and weigh a lot. When dried, this tree is lighter than cork. [12]

6.3 Proverbs and sayings about humidity

A lot of snow means a lot of bread.

Calm water washes away the shores.

Water wears away stones too.

Without a lid, the samovar does not boil; without a mother, a child cannot frolic.

Frozen - like at the bottom of the sea.[11]

DEW On Proklos the field was wet with dew.

In the morning, heavy dew and fog mean good weather.

Abundant dew, day of mourning, great and healing dew.

Morning dew is a kind tear: it washes the forest with it and says goodbye to the night. Evening dew - to a partly cloudy / cloudless / night.

Morning to maintain good weather.

Very heavy dew to bad weather.

Complete absence of dew:

to maintain good weather

to prolonged bad weather

wait for the rain tomorrow

Small drops - expect several amazingly clear nights.

Rising upward - before the rain.

Lying in low-lying places means maintaining (improving) good weather.

Fog at high altitudes means cloudy nights.

Salt gets wet - it means rain.

Tobacco becomes damp - indicates damp weather. The splinter crackles and throws sparks - to bad weather.

If a voice is heard far away in a field, it will rain.

Pots easily boil over the edge - a sign of bad weather.[15]

In winter it warms, in spring it smolders, in summer it dies, in autumn it flies. (Snow.) The world warms, does not know fatigue. (Sun.) How can you carry water in a sieve? (Freezing the water.)[11]

Measuring air humidity in the office.

Purpose: measure the humidity in the room using two thermometers.

The room temperature is measured using a conventional mercury thermometer and recorded. Then the head of the thermometer must be tightly wrapped in wet gauze or cotton wool and after 10 minutes measure the temperature again. Now we subtract the temperature of the “wet” thermometer from the temperature of the “dry” thermometer, and using a special table we determine the air humidity in the room using the temperature difference.

By the end of lesson 6, the air humidity in the classroom exceeds the norm.

Decorating a flower garden in the office.

In my essay, I tried to consider what changes in humidity occur in the Earth’s atmosphere, its characteristics, its impact on human life, on the formation of the climate on the planet. I learned a lot about low humidity and its consequences. It was very interesting for me to get acquainted with the instruments used to measure air humidity.

While working on my essay, I discovered many new and useful facts. For example, I learned that a person feels comfortable at a humidity of 60-70%, but at 30% he becomes ill, his health worsens, and various diseases and allergies develop. I began to monitor the humidity in my home so as not to risk my health.

I read a lot of literature on air humidity and found out that it can cause enormous damage to our planet. Humidity can radically change the climate on Earth, and after some time it will increase several times.

I learned that humidity affects almost everything that surrounds us. It has a destructive effect on books, buildings, server rooms, and the climate.

I was very interested to learn about how plants adapt to climatic conditions on Earth, what effect humidity has on them, how to care for them during periods of low or high humidity. I also learned that a plant is the very first assistant in determining the air humidity in a room.

I really enjoyed working on the chosen essay topic. I learned a lot of new and interesting things about air humidity and I believe that humidity is the most important thing that surrounds us.

Brilev D.V. Physics. LLC "TD "Publishing World of Books" 2006

Katz Ts.B. Biophysics in physics lessons. Publishing house "Prosveshcheniye" 1974

Kuprin M.Ya. Physics in agriculture. Publishing house "Prosveshcheniye" 1985

Ryzhenkov A.P. Physics. Human. Environment. Publishing house "Prosveshcheniye" 1996

Perelman Ya.I. Entertaining physics. Publishing house "Science" 1986

Air humidity throughout the year in different parts of the world

Relative humidity, %

Central Russia

1 . with air conditioning (summer-autumn)

2. with central heating (winter-spring)

Elements of water balance

Volume, thousand km 3 /year

Vessels and capillaries in wood

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    Source: http://school-science.ru/2/11/30427